Photographic systems capture a series of images on strips of sensitized film. After exposure, the film strip is chemically processed to develop a stable negative images on the film. These film strips are passed through printers that serially focuses each image onto a matching area on a strip of photosensitive paper. Each image is pre-analyzed for density and color balance, and the exposure of the film image onto the paper is controlled to correct for errors in film density and film color balance.
Film writers create continuous tone images on film by moving a modulated beam of light across the film. Three light emitting diodes can generate a beam of modulated red green and blue light that is moved across the film as a series of stripes. As the beam is moved, the intensity of the light is modulated to create pixels of varying density onto the film. Sequential stripes are written to create a two dimensional photographic image on the film.
Film scanners sequentially passes a beam of light in stripes across exposed and developed film. Sensors measure the intensity of the beam that is transmitted through the negative image to measure the density of the image on the film. The measurement of red, green and blue spectra of light passing through the film is used to create a digital representation of the image on the film.
The Advanced Photographic System from Kodak describes a system that spools the strip of light sensitive emulsion into a light tight cartridge. The cartridges are used to store both developed and unexposed film strips. The spool is positioned within the cartridge to indicate whether the type of film in the cartridge is developed or unexposed.